Flashback device for venous specimen collection

1. Field of the Invention

0001The present invention relates to a needle assembly having a needle cannula, a hub to which the needle cannula is mounted and a safety shield that can be telescoped from a proximal position where the needle cannula is exposed to a distal position where the needle cannula is safely shielded. The needle assembly also includes a flashback indicator to indicate successful venous entry.

2. Description of the Related Art

0002A typical needle assembly includes a needle cannula having a proximal end, a pointed distal end and a lumen extending between the ends. A thermoplastic hub is mounted securely to the needle cannula at a location spaced from the distal end. The hub is provided with external threads or other surface configurations for removably mounting the prior art needle cannula on another structure. Some needle assemblies are used for drawing a sample of blood or other body fluid from a patient. The needle cannulas for these assemblies typically have pointed proximal and distal ends, and the needle hub is mounted to a location between the opposed ends of the needle cannula.

0003A needle assembly that is used to draw a sample of blood or other bodily fluid typically is used with a needle holder. The needle holder has a substantially tubular sidewall with a widely opened proximal end and a partly closed distal end. The hub of the prior art needle assembly can be engaged releasably with the partly closed distal end of the needle holder. Thus, the pointed proximal end of the needle cannula projects into the needle holder, while the pointed distal end of the needle cannula projects distally beyond the needle holder.

0004The combination of a needle assembly and a needle holder is used with an evacuated tube for drawing a sample of blood or other bodily fluid from a patient. The tube has a closed end, an open end, and a sidewall extending between the ends. The tube is evacuated, and the open end is sealed by a septum that retains the vacuum within the tube. The evacuated tube is dimensioned to be slid into the open proximal end of the needle holder. Sufficient sliding of the evacuated tube into the needle holder causes the proximal point of the needle cannula to pierce the septum of the evacuated tube. Thus, the needle cannula can be placed in communication with the interior of the evacuated tube.

0005The combination of a needle assembly, a needle holder and an evacuated tube is employed by initially urging the pointed distal end of the needle cannula into a blood vessel of a patient. Once the targeted blood vessel has been reached, the evacuated tube is urged into the needle holder so that the proximal point of the needle cannula pierces the septum on the tube. Low pressure conditions within the evacuated tube generate a flow of blood from the patient through the needle cannula and into the evacuated tube. The evacuated tube may be removed from the needle holder after a sufficient quantity of blood has been collected. One or more additional evacuated tubes may similarly be urged into the open end of the needle holder for drawing one or more additional samples of blood to be analyzed.

0006The needle cannula is withdrawn from the patient after a sufficient volume of blood has been collected for the required analytical procedures. The used needle cannula then must be shielded properly to avoid an accidental stick that could transmit a disease from the patient to the medical practitioner.

0007Many types of devices are available for shielding a used needle cannula. Some shields are hinged to the needle hub, and can be rotated from a first position, where the hinged shield is spaced from the needle cannula for use. After use, the hinged shield is rotated to a second position in shielding engagement around the needle cannula.

0008Other shields are telescoped over both the needle cannula and the needle hub. These shields initially are retained in a proximal position where the shield covers the hub but exposes the needle cannula for use. After use, the shield is telescoped distally to cover the needle cannula.

0009Most shielded needle assemblies are effective at performing their primary function of shielding a used needle cannula. However, many medical practitioners consider the available shieldable needle assemblies cumbersome. In particular, the shield that is telescoped over the needle hub typically will move relative to the needle cannula. Consequently, medical practitioners will grip the needle holder or other medical implement to which the shieldable needle assembly is mounted. However, a gripable region on the needle holder typically is relatively far from the distal end of the needle cannula and leads to at least a perception of poor control of the needle cannula. The perception of poor control increases as the length of the needle cannula is increased. As a result, needle assemblies with shields that telescope over the needle hub necessarily impose a limit on the length of the needle cannula that can be employed.

0010Additionally, in some cases, practitioners may be rushing and forget to operate the safety shield. Other situations arise where the patient moves suddenly or unexpectedly. Thus the needle cannula may inadvertently be pulled out of the vein and exposed with no time for the phlebotomist to initiate safety shielding. These weaknesses are not addressed adequately in prior art devices.

0011Another problem with many prior art blood collection devices relates to the time required to assure venous entry. In particular, blood will begin to flow through the cannula upon entry of the intravenous or distal end of the cannula into the vein. However air that had been in the cannula and in the multiple sample sleeve that covers the non-patient end of the cannula will resist the flow of blood into and through the cannula. The medical practitioner will urge an evacuated tube into the needle holder once the practitioner is reasonably sure that the vein has been entered. The rubber stopper at the end of the evacuated tube will deform the multiple sample sleeve over the non-patient end of the cannula and will permit the non-patient end of the cannula to enter the evacuated tube. The pressure differential between the evacuated tube and the cannula will cause the blood to flow into the evacuated tube. This often provides the first visual assurance that the vein has been accessed properly. There are many instances where a medical practitioner will properly access a vein with the distal end of the needle cannula, but will mistakenly believe that the vein has not been entered. Hence, the practitioner will make a second attempt to access the vein. This adds to the discomfort for the patient, extends the time to carry out a blood collection procedure and increases the risk for an accidental stick with a cannula that has been exposed to the patient's blood. Additionally, in some instances a passive shielding mechanism will be activated when the cannula is withdrawn from the patient, thereby making the needle cannula unusable and requiring the medical practitioner to obtain a new needle assembly.

0012Some needle assemblies are provided with flashback chambers. Flashback chambers include a transparent or translucent housing near the proximal end of a needle cannula. The flashback chamber is intended to provide an early indication of venous entry. Flashback chambers, however, have not been employed in needle assemblies that incorporate passively activated shields.

0013A medical device of the type defined in the first part of claim 1 is disclosed in <patcit id="pcit0001" dnum="US4444203A"><text>U.S. 4,444,203 A</text></patcit>. This medical device is an intravenous catheter insertion set comprising a proximal needle and a distal needle which are connected by a flashback chamber formed in a housing. The housing comprises a transparent wall having a vent hole. The vent hole is covered by a cover that selectively allows air to flow in one direction, namely away from the flashback chamber. Manual pressure against the cover will seal the vent hole and prevent air from being drawn into the chamber. This medical device does not have a safety shield.

0014A medical device comprising a safety shield is disclosed in <patcit id="pcit0002" dnum="US20030093009A1"><text>US 2003/0093009 A1</text></patcit>. The safety shield is moved distally by a spring upon releasing of a trigger, thus covering and shielding a distal needle. This medical device does not have a flashback chamber.

0015<patcit id="pcit0003" dnum="WO0056214A"><text>WO 00/56214</text></patcit> discloses a blood sampling device comprising a patient cannula connected to a flashback chamber. A second cannula to be connected with a blood collection tube extends at an obtuse angle from the patient cannula. The patient cannula and the second cannula are in fluid communication via the flashback chamber.

SUMMARY OF THE INVENTION

0016The present invention is directed to a needle assembly with means for shielding the user or patient end of the needle cannula. The medical device of the invention is defined by claim 1. The needle assembly includes a needle cannula having opposed proximal and distal ends and a lumen extending between the ends. At least the distal end of the needle cannula may be pointed.

0017The needle assembly further includes a hub surrounding portions of the needle cannula. The hub includes opposed proximal and distal ends that are disposed between the proximal and distal ends of the needle cannula. The hub may be mounted securely to the needle cannula. Additionally, the proximal end of the hub may be provided with external structure for releasable engagement with a needle holder or with some other medical implement.

0018The needle assembly further includes a housing that may be attached to the hub. The primary function of the housing is to provide guidance for a shield telescoped between the needle cannula and hub. The housing partially encloses the shield and constrains shield motion in a longitudinal direction, substantially co-axial with the needle cannula. Additionally, the housing further includes external surface configurations to assist the user in manipulating the device during venous punctures. The housing may have external structure for releasable engagement with a needle holder or with some other medical implement.

0019The above-referenced shield of the needle assembly surrounds the needle cannula and is telescoped into the housing. The shield initially is retained in a proximal position such that distal portions of the needle cannula are exposed for use. The shield can be moved from the proximal position to a distal position where the shield surrounds at least the pointed distal end of the needle cannula. The shield preferably is dimensioned to cover all of the needle cannula between the housing and the distal end of the needle cannula. Additionally, the shield preferably is constructed for locking engagement with the housing when the shield is in its distal position. Thus, the needle cannula cannot be re-exposed after shielding.

0020The needle assembly may further include biasing means for urging the shield from the proximal position to the distal position. The biasing means may comprise a coil spring disposed within the housing and extending between a portion of the hub and a portion of the shield. The spring may be in a compressed condition when the shield is in its proximal position. The spring then is operative to propel the shield to the distal position.

0021Actuating means are provided for releasing the shield from the proximal position and enabling the biasing means to propel the shield to the distal position. The actuating means may be actuated automatically and passively in response to an operational condition indicative of use of the needle assembly. For example, the needle assembly intended for use with an evacuated tube may have an actuating means that is triggered by the movement of the evacuated tube into communication with the proximal end of the needle cannula. Alternatively, the actuating means may comprise a latch that is accessible at an external location such as on the hub or housing.

0022The needle assembly of the present invention enables a medical practitioner to hold portions of the housing that surround the shield during venipuncture. Thus, the medical practitioner is able to grip a portion of the needle assembly relatively close to the distal end of the needle cannula. Gripping may be facilitated by structural elements disposed externally on the housing. Thus, for example, the housing may include at least one flat dimensioned and disposed for convenient gripping. Alternatively, the housing or hub may be provided with corrugations, dimples, recesses, concave surfaces, roughening or other structure that will facilitate manual gripping by a medical practitioner.

0023The needle assembly of the subject invention is configured to provide an early indication of venous access. The hub of the needle assembly for providing an indication of venous access includes a flashback chamber that may be formed at least partly from a transparent or translucent material. The needle cannula of this embodiment may include an intravenous cannula and a non-patient cannula. The intravenous cannula preferably includes a proximal end securely mounted in the hub and communicating with the flashback chamber. The intravenous cannula further includes a pointed distal end that projects distally beyond the hub. The non-patient cannula preferably includes a distal end securely mounted in the hub and communicating with the flashback chamber. The non-patient cannula further includes a proximal end that projects proximally beyond the hub. Alternatively, a single cannula can be provided with a transverse aperture that communicates with the flashback chamber.

0024The hub of the needle assembly for providing an early indication of venous access further includes a vent that communicates with the flashback chamber. For example, the hub may be molded to include a vent aperture and a vent plug may be mounted securely in the vent aperture. The plug may include micro-holes that are large enough to allow air to escape from the flashback chamber. However, the micro-holes will not permit a flow of blood or other liquid through the plug. The plug may be molded from a transparent or translucent material or may include a transparent or translucent portion.

0025Other aspects of the needle assembly of this alternate embodiment, including the shielding features, may be substantially the same as the above-described embodiments. With this embodiment, however, the flashback chamber provides an early indication of venous access. Specifically, venous access will permit blood to flow through the intravenous cannula. The pressure of the flowing blood will cause air in the intravenous cannula and in the flashback chamber to flow through the micro-pores in the vent plug and into the surrounding atmosphere. Hence, blood will continue to flow substantially unimpeded through the intravenous cannula and into the flashback chamber. The blood in the flashback chamber will be visible through the transparent or translucent walls of the hub or the vent plug. An evacuated tube then can be placed in communication with the proximal end of the non-patient cannula, substantially as described above. One or more tubes of blood can be collected as described above. Additionally, the shield preferably is actuated substantially as described above. Thus, this embodiment of the invention preferably has the advantages of the previous embodiments relating to passive shielding, but also provides an early indication of venous access.

DESCRIPTION OF THE DRAWINGS

0026<figref idref="f0001">FIG. 1</figref> is a perspective view of a needle assembly not belonging to the present invention.

0027<figref idref="f0002">FIG. 2</figref> is an exploded view of the device shown in <figref idref="f0001">FIG. 1</figref>.

0028<figref idref="f0003">FIG. 3</figref> is a perspective view with the packaging shield covering the needle cannula before use.

0029<figref idref="f0004">FIG. 4</figref> is a perspective of <figref idref="f0001">FIG. 1</figref> with the needle shield covering the needle cannula after use.

0030<figref idref="f0005">FIG. 5</figref> is an exploded view of the cannula and hub sub-assembly as it fits within the housing and holder sub-assembly.

0031<figref idref="f0005">FIG. 6</figref> is a partially exploded view of the cannula and hub sub-assembly aligned for assembly with the housing.

0032<figref idref="f0006">FIG. 7</figref> is a magnified view of the portion of <figref idref="f0005">FIG. 6</figref> showing the proximal end of the housing with snap retainers.

0033<figref idref="f0007">FIG. 8</figref> is an exploded perspective view of a needle assembly with detached holder of the present invention.

0034<figref idref="f0007">FIG. 9</figref> is an exploded perspective view of the needle assembly in <figref idref="f0007">FIG. 8</figref> with non-patient shield detached.

0035<figref idref="f0006">FIG. 10</figref> is an exploded perspective view of the needle assembly in <figref idref="f0007">FIG. 8</figref> with the packaging and non-patient shields removed from the housing.

0036<figref idref="f0008">FIG. 11A</figref> is a front view of the housing.

0037<figref idref="f0008">FIG. 11B</figref> is a sectional perspective view of the housing cut along the line depicted in <figref idref="f0008">FIG. 11A</figref>.

0038<figref idref="f0008">FIG. 11C</figref> is a sectional perspective view of the housing cut along the line depicted in <figref idref="f0008">FIG. 11A</figref>.

0039<figref idref="f0008">FIG. 12A</figref> is perspective view of the safety shield.

0040<figref idref="f0009">FIGS. 12B</figref> is an elevational view of the safety shield of the present invention.

0041<figref idref="f0009">FIG. 12C</figref> is an elevation view of the safety shield of the present invention with the deflectable member in an unbiased position.

0042<figref idref="f0009">FIG. 12D</figref> is an elevation view of the safety shield similar to <figref idref="f0009">FIG. 12C</figref>, but with the deflectable member in a deflected state.

0043<figref idref="f0010">FIG. 13</figref> is an elevation view of the actuator .

0044<figref idref="f0010">FIG. 14</figref> is a perspective view of the actuator.

0045<figref idref="f0011">FIG. 15</figref> is a perspective view of the hub.

0046<figref idref="f0011">FIG. 16</figref> is an elevation view of the hub of <figref idref="f0011">FIG. 15</figref>.

0047<figref idref="f0012">FIG. 17</figref> is an elevation view of the needle assembly during use before shielding.

0048<figref idref="f0012">FIG. 18</figref> is an elevation view of the needle assembly after shielding.

0049<figref idref="f0013">FIG. 19A</figref> is a sectional view of the present invention shown before actuator safety shield release.

0050<figref idref="f0013">FIG. 19B</figref> is a sectional view of the present invention shown during actuator safety shield release.

0051<figref idref="f0014">FIG. 19C</figref> is a sectional view shown after actuator safety shield release but prior to complete shielding.

0052<figref idref="f0014">FIG. 19D</figref> is a sectional view of the present invention shown after actuator safety shield release and after complete shielding.

0053<figref idref="f0015">FIG. 20A</figref> is a perspective sectional view shown before actuator safety shield release.

0054<figref idref="f0015">FIG. 20B</figref> is a perspective sectional view shown during actuator safety shield release.

0055<figref idref="f0016">FIG. 20C</figref> is a perspective sectional view shown alter actuator safety shield release but prior to complete shielding.

0056<figref idref="f0016">FIG. 20D</figref> is a perspective sectional view shown alter actuator safety shield release and alter complete shielding.

0057<figref idref="f0017">FIG. 21</figref> is a perspective view of an alternate needle assembly not belonging to the present invention prior to use and with the packaging shield covering the needle cannula.

0058<figref idref="f0018">FIG. 22</figref> is an exploded perspective view similar to <figref idref="f0002">FIG. 2</figref>, but showing the alternate embodiment of <figref idref="f0017">FIG. 21</figref>.

0059<figref idref="f0019">FIG. 23</figref> is a cross-sectional view taken along line 23-23 in <figref idref="f0017">FIG. 21</figref>.

0060<figref idref="f0020">FIG. 24</figref> is a perspective view of the holder for use with the embodiment of <figref idref="f0017 f0019">FIGS. 2123</figref>.

0061<figref idref="f0021">FIG. 25</figref> is a perspective view of the hub for use with the embodiment of <figref idref="f0017 f0018 f0019 f0020">FIGS. 21-24</figref>.

0062<figref idref="f0022">FIG. 26</figref> is a side elevational view of the actuator of the embodiment of <figref idref="f0017 f0018 f0019 f0020 f0021">FIGS. 21-25</figref>.

0063<figref idref="f0023">FIG. 27</figref> is a perspective view of the actuator of <figref idref="f0022">FIG. 26</figref>.

0064<figref idref="f0024">FIG. 28</figref> is a perspective view of an alternate embodiment of the actuator that permits both manual actuation and tube actuation of the shield.

0065<figref idref="f0025">FIG. 29</figref> is an exploded perspective view of a needle assembly in accordance with the embodiment of the invention.

0066<figref idref="f0026">FIG. 30</figref> is an exploded longitudinal cross-sectional view of the needle assembly shown in <figref idref="f0025">FIG. 29</figref>.

0067<figref idref="f0027">FIG. 31</figref> is a longitudinal cross-sectional view of the needle assembly of <figref idref="f0025">FIGS. 29</figref> and <figref idref="f0026">30</figref>, but showing a fully assembled condition.

DETAILED DESCRIPTION

0068The needle assembly <b>10</b> is shown in <figref idref="f0001 f0002 f0003 f0004 f0005 f0006">FIGS. 1-7</figref> and <figref idref="f0008 f0016">11-20</figref>. It will be noted that the term "distal" as used herein refers to the end of the needle assembly that punctures the patient's skin while "proximal" means the end of the needle assembly that punctures an evacuated container. Needle assembly <b>10</b> is mounted to a needle holder <b>12,</b> as shown in <figref idref="f0001">FIGS. 1</figref>, <figref idref="f0003">3</figref>, and <figref idref="f0004">4</figref>. Needle holder <b>12</b> has a proximal end <b>14,</b> a distal end <b>16</b> and a tubular sidewall <b>18</b> extending between ends <b>14</b> and <b>16.</b> Proximal end <b>14</b> of needle holder <b>12</b> is widely open and is adapted to receive a blood collection tube <b>20</b> as shown in <figref idref="f0012">FIGS. 17</figref>, <figref idref="f0013 f0014">19A-19D</figref>, and <figref idref="f0015 f0016">20A-20D</figref>. However, proximal end <b>14</b> of holder <b>12</b> may have a removable seal or cap <b>15</b> for sterility. Proximal end <b>14</b> of holder <b>12</b> also has a radially aligned finger flange <b>17</b> to facilitate manipulation of holder <b>12.</b> Flange <b>17</b> is non-circular to prevent holder <b>12</b> from rolling. Flange <b>17</b> preferably has a linear edge to provide a clear indication of the top and bottom sides. Distal end <b>16</b> of needle holder <b>12</b> includes structure to which needle assembly <b>10</b> is mounted. In particular, distal end <b>16</b> of needle holder <b>12</b> may be formed with non-threaded mounting means, such that needle holder <b>12</b> is substantially fixed to needle assembly <b>10</b> after assembly. The non-threaded mounting means comprises a combination of external rings <b>81</b> and keyways to secure needle assembly <b>10</b> axially and circumferentially. It is preferred that needle assembly <b>10</b> is mounted to needle holder <b>12</b> by the manufacturer so that the device is ready for fast and convenient use. Most importantly, pre-assembled needle assemblies <b>10</b> and needle holders <b>12</b> ensure that the proximal point of the needle is enclosed within holder <b>12</b> before, during, and after blood collection. Alternately, however, the distal end of the needle holder may be formed with an internal array of threads that are engagable by external threads on the needle assembly.

0069Needle assembly <b>10</b> ideally is packaged in a blister package having a thermoformed blister and top web. The top web is comprised of a material that may be permeable to gas such as ethylene oxide gas. Optionally, the proximal end <b>14</b> of holder <b>12</b> can be covered with a paper-like membrane that is thermally or adhesively sealed onto the proximal end <b>14</b> of the holder. Examples of materials used for a paper-like membrane are Tyvek® manufactured by DuPont and examples of materials to be used for a thermoformed blister package include glycol modified polyethylene terephthalate (PETG), polyethylene terephthalate (PET), high-density polyethylene, polypropylene, polycarbonate, nylon, and K-resin. In the configuration with a paper-like membrane covering the open proximal end <b>14</b> of holder <b>12,</b> a thermoformed blister and top web would not be required, and the entire assembly can be sterilized by ethylene oxide gas or cobalt 60 irradiation.

0070Needle assembly <b>10</b> includes a needle cannula <b>22,</b> a needle hub <b>24,</b> a packaging shield <b>26,</b> a safety shield <b>28,</b> a sleeve <b>39,</b> a housing <b>80,</b> an actuator <b>30,</b> and a spring <b>32.</b> In other embodiments, a portion of the needle assembly (e.g., the housing) can be integral or unitary with the needle holder to reduce assembly steps by the manufacturer and the user.

0071Needle cannula <b>22</b> includes a pointed proximal end <b>34,</b> as shown in <figref idref="f0001">FIGS. 1</figref>, <figref idref="f0005">5 and 6</figref>, a sharply beveled distal end <b>36</b> and a lumen <b>38</b> extending therebetween. Proximal end <b>34</b> of needle cannula <b>22</b> is covered by an elastomeric multiple sample sleeve <b>39</b> (shown in <figref idref="f0002">FIGS. 2</figref>, <figref idref="f0007">9</figref> and <figref idref="f0006">10</figref>) that can be pierced by pointed proximal end <b>34</b> of needle cannula <b>22.</b>

0072Needle hub <b>24</b> is illustrated in greater detail in <figref idref="f0011">FIGS. 15 and 16</figref>. Needle hub <b>24</b> includes a proximal end <b>40,</b> a distal end <b>42,</b> and a lumen <b>38</b> extending therebetween. Housing attachment means is provided externally of hub <b>24</b> to achieve fixed engagement between hub <b>24</b> and needle housing <b>80.</b> The housing attachment means may include ultrasonic welding, heat staking, solvent bonding, mechanical latches with receiving latch detents, adhesive bonding, friction fit joints, irreversible threads, or any of the like. In the embodiment of <figref idref="f0005">FIGS. 5, 6</figref>, <figref idref="f0006">7</figref>, <figref idref="f0011">15 and 16</figref> the housing attachment means are defined by mechanical latches <b>86</b> that extend distally from needle hub <b>24</b> for engagement in detents <b>88</b> on needle housing <b>80.</b> Hub <b>24</b> is mounted securely to locations on needle cannula <b>22</b> between proximal and distal ends <b>34</b> and <b>36</b> thereof and in a specified rotational orientation relative to the bevel at distal end <b>36</b> of needle cannula <b>22.</b> More particularly an adhesive well is formed on needle hub <b>24</b> and receives adhesive to bond needle cannula <b>22</b> to hub <b>24.</b> Alternately, needle hub <b>24</b> and needle housing <b>80</b> may be combined as one molded component. However it is generally easier to manufacture needle hub <b>24</b> and housing <b>80</b> as two components.

0073Needle housing <b>80</b> is illustrated in greater detail in <figref idref="f0008">FIGS. 11A-11C</figref>. Needle housing <b>80</b> includes a proximal end <b>82,</b> a distal end <b>84</b> and a tubular wall <b>44</b> extending between ends <b>82</b> and <b>84.</b> As shown in <figref idref="f0008">FIGS. 11A-11C</figref>, tubular wall <b>44</b> is of generally circular or elliptical cross-section. Alternately, tubular wall <b>44</b> may have a non-circular cross-section or rectangular cross-section. The specific cross-sectional shape is not critical, and shapes other than those shown herein are contemplated. Housing <b>80</b> preferably is formed from a transparent or translucent material to permit user observation of safety shield <b>28.</b> Thus, the medical practitioner can observe movement of safety shield <b>28,</b> as explained below, to provide a visual indication that proper shielding is taking place. Additionally, proximal end <b>82</b> of housing <b>80</b> may have one of many optional means for attachment to a needle holder <b>12,</b> such as a threaded connection, interference fit, adhesive bonding, solvent bonding, ultrasonic welding, heat staking, snap fit, or any other means. More specifically, the housing may have external threads and may be mounted to internal threads of the distal end of the needle holder. Alternately, housing <b>80</b> has non-threaded mounting means to engage holder <b>12</b> in an interlocking manner. External rings <b>81</b> are illustrated in <figref idref="f0005 f0006">FIGS. 5-7</figref> and define one preferred non-threaded mounting means that provide sufficient frictional or interlocking forces to resist housing <b>80</b> from unintentionally releasing from holder <b>12</b> during puncturing of septum <b>21</b> by proximal end <b>34</b> of needle cannula <b>22.</b> In the illustrated embodiment, hub <b>24</b> is mounted indirectly to the holder <b>12</b> through needle housing <b>80.</b> Housing <b>80</b> preferably is non-rotatably mounted to holder <b>12</b> to ensure that the bevel at distal end of needle cannula <b>22</b> faces up relative to the bottom edge of flange <b>17</b> of holder <b>12.</b> Distal end <b>84</b> of needle housing <b>80</b> is characterized by diametrically opposed V-shaped notches as shown in <figref idref="f0008">FIG. 11B</figref>. Notches <b>85</b> cooperate with corresponding structure on packaging shield <b>26.</b>

0074Housing <b>80</b> has a length such that distal end <b>84</b> of housing <b>80</b> is spaced proximally from distal end <b>36</b> of needle cannula <b>22</b> sufficiently to enable convenient use of needle cannula <b>22.</b> Portions of tubular wall <b>44</b> from distal end <b>84</b> toward proximal end <b>82</b> of hub <b>24</b> are spaced outwardly from needle cannula <b>22</b> for permitting telescoped movement of safety shield <b>28</b> between needle cannula <b>22</b> and housing <b>80,</b> as explained further below. Additionally, as shown in <figref idref="f0001">FIGS. 1</figref>, <figref idref="f0003">3</figref>, and <figref idref="f0004">4</figref>, tubular sidewall <b>44</b> of housing <b>80</b> is provided with external surface configurations or grips <b>46</b> to facilitate digital manipulation. Surface configurations or grips <b>46</b> include elongate recesses or flats having small bumps thereon. However, other surface configurations may be employed, such as a plurality of ridges or grooves, or concave detents shaped to conform to a user's fingers. Grips <b>46</b> preferably are orthogonal to the bottom edge of finger flange <b>17</b> of holder <b>12.</b>

0075Housing <b>80</b> has internal features to restrict movement of safety shield <b>28</b> relative to housing <b>80.</b> Tubular wall <b>44</b> of housing <b>80</b> is formed with a first proximal facing stop surface <b>48.</b> As shown in <figref idref="f0008">FIG. 11B</figref>, housing <b>80</b> further includes an axially extending latch channel <b>52</b> formed on an upper interior surface of tubular wall <b>44.</b> Latch channel <b>52</b> extends from the first proximal facing stop surface <b>48</b> shown in <figref idref="f0008">FIG. 11C</figref> to a location substantially adjacent distal end <b>84</b> of housing <b>80</b> as shown in <figref idref="f0008">FIG. 11B</figref>. A distal detent <b>47</b> is located near the distal end of tubular wall <b>44</b> of housing <b>80,</b> as shown, and is at the distal end of latch channel <b>52.</b> Distal detent <b>47</b> has a distally facing stop surface <b>54.</b> Distal detent <b>47</b> and distally facing stop surface <b>54</b> are dimensioned to receive a latch <b>68</b> on safety shield <b>28,</b> as explained below. Tubular wall <b>44</b> further includes a stop channel <b>50</b> extending distally and ending with a second proximally facing stop surface <b>58</b> near distal end <b>82</b> of housing <b>80</b> as shown in <figref idref="f0008">FIG. 11C</figref>.

0076Distal end <b>36</b> of needle cannula <b>22</b> is used to pierce the patient's skin and must be kept very sharp. Thus a packaging shield <b>26,</b> as shown in <figref idref="f0001 f0002 f0003">FIGS. 1-3</figref> and <figref idref="f0007 f0006">8-10</figref>, is used to enclose the distal end <b>36</b> of needle cannula <b>22.</b> The packaging shield <b>26</b> preferably is formed with two opposing relatively flat walls <b>19</b> to facilitate easy handling by the phlebotomist who is likely to be wearing gloves that may even be wet with alcohol prep solution. In the embodiment shown, the open end of the packaging shield <b>26</b> fits partially over the distal end <b>84</b> of housing <b>80.</b> The packaging shield <b>26</b> and housing <b>80</b> are dimensioned so that there is an interference fit that desirably provides a sterile barrier between the packaging shield <b>26</b> and housing <b>80</b> in those embodiments that do not employ blister packaging. In those embodiments, the interference fit between packaging shield <b>26</b> and housing <b>80</b> they make separation of packaging shield <b>26</b> difficult. Accordingly, for those embodiments, packaging shield <b>26</b> is provided with a pair of diametrically opposed ribs (not shown) on the interior surface. The ribs terminate at a V-shaped point or an arcuate end facing toward the open end of packaging shield <b>26.</b> The ends of the ribs are disposed, dimensioned and configured to mate with the V-shaped notches <b>85</b> at distal end <b>84</b> of housing <b>80.</b> The engagement of the ends of the rib with V-shaped notches <b>85</b> develops ramping forces in response to twisting of packaging shield <b>26.</b> Thus, the rotational movement applied to packaging shield <b>26</b> generates a corresponding axial movement of packaging shield <b>26</b> relative to housing <b>80,</b> and hence facilitates separation of packing shield <b>26.</b> Additionally, a tamper-evidence indicator may be placed between the packaging shield <b>26</b> and the housing <b>80</b> to provide indication of prior usage.

0077Safety shield <b>28,</b> as shown in <figref idref="f0008 f0009">FIGS. 12A-12D</figref>, includes a proximal end <b>60,</b> a distal end <b>62</b> and a substantially tubular sidewall <b>64</b> extending between the ends. Tubular sidewall <b>64</b> of safety shield <b>28</b> preferably is imprinted with indicia at a location aligned with the bevel-up side of needle cannula <b>22.</b> This is the portion of tubular sidewall <b>64</b> that will be the most visible to the medical practitioner. The existence of indicia on this portion of tubular sidewall provides a physical indication to the medical practitioner that shielding is taking place. The indicia should be in a form that will provide evidence of movement. For example, a plurality of intermittent markings or a marking that changes its dimensions along its length would be most beneficial. Safety shield <b>28</b> initially is retained releasably in a proximal position with at least a major portion of safety shield <b>28</b> disposed in the space between needle cannula <b>22</b> and tubular wall <b>44</b> of housing <b>80.</b> In this proximal position, proximal end <b>60</b> of safety shield <b>28</b> is substantially adjacent first proximally facing stop surface <b>48</b> of housing <b>80.</b> Additionally, as shown in <figref idref="f0001">FIG. 1</figref>, distal end <b>62</b> of safety shield <b>28</b> is flush with or projects only slightly from distal end <b>84</b> of housing <b>80</b> when safety shield <b>28</b> is in its proximal position. Safety shield <b>28</b> can be released from its proximal position and is movable to a distal position that is shown in <figref idref="f0004">FIGS. 4</figref>, <figref idref="f0012">18</figref>, <figref idref="f0014">19D</figref> and <figref idref="f0016">20D</figref>. When moved into its distal position, safety shield <b>28</b> completely covers portions of needle cannula <b>22</b> between needle hub <b>24</b> and distal end <b>36</b> of needle cannula <b>22.</b>

0078As shown in <figref idref="f0009">FIGS. 12 B - 12D</figref>, safety shield <b>28</b> has a hinged deflectable member <b>66</b> that is cantilevered toward proximal end <b>60.</b> Deflectable member <b>66</b> is deflectable outwardly or in a transverse direction. A latch <b>68</b> is formed on deflectable member <b>66</b> near proximal end <b>60</b> of safety shield <b>28</b> and enters latch channel <b>52</b> when deflectable member <b>66</b> is deflected outwardly. Hinged deflectable member <b>66</b> further includes a cam surface <b>70</b> at the extreme proximal end thereof. Cam surface <b>70</b> is aligned at an acute angle to a radial plane passing through needle assembly <b>10.</b> Axially aligned distally directed forces on cam surface <b>70</b> will generate a transverse deflection of deflectable member <b>66</b> so that latch <b>68</b> enters into latch channel <b>52.</b> Latch <b>68</b> further includes a distal facing locking face <b>72,</b> and a proximally facing locking face <b>73.</b> Both locking faces <b>72</b> and <b>73</b> are aligned substantially perpendicular to the axis of needle assembly <b>10.</b><figref idref="f0009">FIG. 12C</figref> shows deflectable member <b>66</b> in its non-deflected state and <figref idref="f0009">FIG. 12D</figref> shows deflectable member <b>66</b> in its deflected state. Distal movement of actuator <b>30</b> moves deflectable member <b>66</b> from the position shown in <figref idref="f0009">FIG. 12C</figref> in direction <b>69</b> depicted in <figref idref="f0009">FIG. 12C</figref> to the position shown in <figref idref="f0009">FIG. 12D</figref> until latch <b>68</b> is no longer resisted by first proximally facing stop surface <b>48</b> of housing <b>80</b> and therefore is free to move distally with respect to the needle cannula <b>22</b> under spring energy supplied by spring <b>32.</b>

0079Safety shield <b>28</b> further includes a stop <b>74</b> disposed substantially diametrically opposite latch <b>66.</b> Stop <b>74</b> is in a plane passing through the axis of needle assembly <b>10</b> and includes a locking surface <b>76</b> facing in the distal direction as shown in <figref idref="f0008">FIG. 12A</figref>. Stop <b>74</b> prevents spring <b>32</b> from pushing safety shield <b>28</b> past housing <b>80.</b>

0080Hub <b>24</b> is connected to the proximal end <b>82</b> of housing <b>80.</b> Hub <b>24</b> further includes an actuator channel <b>56</b> extending substantially parallel to housing <b>80</b> as shown in <figref idref="f0011">FIGS. 15 and 16</figref>. Actuator <b>30,</b> as shown in <figref idref="f0010">FIGS. 13 and 14</figref>, is disposed slidably in actuator channel <b>56</b> of hub <b>24.</b> Actuator <b>30</b> includes a proximal end <b>78</b> substantially adjacent to needle cannula <b>22</b> that will lie within needle holder <b>12.</b> Actuator <b>30</b> also includes a distal end <b>79</b> that will lie substantially adjacent cam surface <b>70</b> of latch <b>68.</b> Distal end <b>80</b> of actuator <b>30</b> is angularly aligned to mate with cam surface <b>70</b> of latch <b>68,</b> such that distal movement of actuator <b>30</b> will generate transverse deflection of deflectable member <b>66.</b>

0081As shown in <figref idref="f0010">FIGS. <b>13</b> and <b>14</b></figref><b>,</b> actuator <b>30</b> has an integrated anti-reset feature or latch <b>29</b> that interfaces with hub <b>24</b> upon activation of the device. Once a tube <b>20</b> is inserted and interfaces with the proximal end <b>78</b> of actuator <b>30,</b> latch <b>29</b> will interface with the hub channel <b>56</b> thus deforming latch <b>29</b> temporarily inward thereby permitting latch <b>29</b> to advance into latch recess <b>23.</b> Once latch <b>29</b> is within latch recess <b>23,</b> latch <b>29</b> will return resiliently towards an undeflected position so that actuator <b>30</b> is prevented from moving back to a proximal position that would allow safety shield 28 to be completely reset to its original position.

0082A spring <b>32</b> surrounds portions of needle cannula <b>22</b> that are surrounded by safety shield <b>28.</b> Thus spring <b>32</b> is compressed to retain stored energy when safety shield <b>28</b> is in the proximal position within tubular wall <b>44</b> of housing <b>80.</b> Spring <b>32</b> then will propel safety shield <b>28</b> distally after activation. The proximal end <b>31</b> of spring <b>32</b> remains in fixed relation to the holder <b>12,</b> hub <b>24,</b> and housing <b>80</b> while the distal end <b>33</b> of spring <b>32</b> moves relative to the holder <b>12,</b> hub <b>24,</b> and housing <b>80.</b>

0083The force applied by spring <b>32</b> to safety shield <b>28</b> is essential to proper operation of needle assembly <b>10.</b> In particular, spring <b>32</b> must exert sufficient force to ensure that safety shield <b>28</b> will be propelled sufficiently toward distal end <b>32</b> of needle cannula <b>22</b> to complete its essential shielding function. However spring <b>32</b> should not exert enough force to push needle cannula <b>22</b> out of the patient. Additionally, forces exerted by safety shields <b>28</b> on the skin of the patient should not be so large as to cause a patient to react and move suddenly away from the shield. A spring force of 0.02-0.20 pounds, and preferably about 0.09 pounds has been found to meet the objectives of ensuring complete shielding without excessive force against the skin of the patient. Additionally, a fine lubricating spray may be applied to the sliding parts of safety shield <b>22,</b> hub <b>24</b> and/or housing <b>80</b> to ensure complete and efficient movement of safety shield <b>28</b> with a low spring force.

0084Needle assembly <b>10</b> is used by attaching proximal end of hub <b>24</b> and housing <b>80</b> into needle holder <b>12</b> such that proximal end <b>23</b> of needle cannula <b>22</b> and proximal end <b>78</b> of actuator <b>30</b> lie within needle holder <b>12.</b> Packaging shield <b>26</b> then is removed from housing <b>80</b> to expose pointed distal end <b>36</b> of needle cannula <b>22.</b> The medical practitioner then manually engages housing <b>80</b> at grips <b>46</b> and guides distal end <b>32</b> of needle cannula <b>22</b> into a targeted vein of a patient. Activation of shield <b>28</b> is achieved automatically and passively by insertion of blood collection tube <b>20</b> into proximal end <b>14</b> of needle holder <b>12.</b> Sufficient insertion of blood collection tube <b>12</b> will cause proximal end <b>34</b> of needle cannula <b>22</b> to pierce through the elastomeric septum <b>21</b> that extends across the open end of blood collection tube <b>20,</b> as shown in <figref idref="f0013 f0014">FIGS. 19A-19D</figref>. Distal movement of blood collection tube <b>20</b> into needle holder <b>12</b> also will cause blood collection tube <b>20</b> to engage proximal end <b>78</b> of actuator <b>30,</b> thereby causing actuator <b>30</b> to slide distally through actuator channel <b>56</b> of hub <b>24.</b> This distal movement of actuator <b>30</b> will cause distal end <b>79</b> of actuator <b>30</b> to engage cam surface <b>70</b> of hinged deflectable member <b>66</b> of safety shield <b>28</b> with sufficient force to pivot deflectable member <b>66</b> transversely about hinge <b>67</b> sufficiently to disengage locking face <b>72</b> of latch <b>66</b> from first proximally facing stop surface <b>48</b> of housing <b>80.</b>

0085Disengagement of latch <b>68</b> from first proximally facing stop surface <b>48</b> into latch channel <b>52</b> causes safety shield <b>28</b> to be propelled distally under the action of spring <b>32.</b> Latch <b>68</b> will be guided in latch channel <b>52</b> as safety shield <b>28</b> is moved toward distal end <b>84</b> of housing <b>80.</b> Sufficient distal movement of safety shield <b>28</b> will cause latch <b>68</b> to engage in distal detent <b>47</b> of housing <b>80.</b> While in distal detent <b>47,</b> latch <b>68</b> interferes with distal facing stop surface <b>54</b> and prevents safety shield <b>28</b> from being unshielded. Additionally, stop <b>74</b> on safety shield <b>28</b> rides along stop channel <b>50</b> until stop <b>74</b> engages second proximally facing stop surface <b>58</b> thereby preventing safety shield <b>28</b> movement in the distal direction after needle point <b>36</b> has been shielded. As a result of stop <b>74</b> and latch <b>68,</b> safety shield <b>28</b> is prevented from moving either distally or proximally from this locked position as shown in <figref idref="f0012">FIGS. 18</figref>, <figref idref="f0014">19D</figref>, and <figref idref="f0016">20D</figref>.

0086The above-described needle assembly is completely passive in that shielding is achieved without any required user activation other than the normal insertion of a fluid collection tube into the open proximal end <b>14</b> of holder <b>12.</b> There may be instances, however, where a user may want direct control over the initiation of shielding or where a user may want dual control where shielding can be actuated by insertion of a fluid collection tube and/or by direct digital activation by the user. These options can be achieved without a complete redesign of the above-described needle assembly. In particular, an alternate needle assembly is identified generally by the numeral <b>10a</b> in <figref idref="f0009 f0010 f0011 f0012 f0013 f0014 f0015 f0016 f0017 f0018 f0019 f0020 f0021 f0022">FIGS. 12-26</figref>. Assembly <b>10a</b> include a needle cannula <b>22,</b> a hub <b>24,</b> a packing shield <b>26</b> and a housing <b>80,</b> all of which are substantially identical to corresponding parts of the first embodiment described and illustrated above. However, assembly <b>10a</b> includes a holder <b>12a</b> that is slightly different from holder <b>12</b> described and illustrated above. In particular, as shown most clearly in <figref idref="f0018">FIGS. 22</figref> and <figref idref="f0019">23</figref>, holder <b>12a</b> includes a tubular sidewall <b>18a</b> that has a proximal end <b>14a,</b> a distal end <b>16a,</b> and a tubular sidewall <b>18a.</b> A notch <b>17a</b> extends into tubular sidewall <b>18a</b> at distal end <b>16a.</b> Additionally, notch <b>17a</b> is disposed on a portion of sidewall 18a that will align with the bevel-up side of needle cannula <b>22.</b> Notch <b>17a</b> is partly surrounded by an elongate flat or recess <b>19a</b> in tubular sidewall <b>18a</b> to minimize the projection of an actuator, as explained herein and to provide a visible indication of a region to be accessed by a user for carrying out a manual actuation of the shielding.

0087Needle assembly <b>10a</b> further includes an actuator <b>30a</b> that differs from actuator <b>30</b> described and illustrated above. In particular, actuator <b>30a</b> includes an actuating beam <b>31a</b> with a distal end <b>79a</b> that is structurally and functionally virtually identical to distal end <b>79</b> of actuator <b>30</b> described above and illustrated in <figref idref="f0010">FIGS. 13 and 14</figref>. Additionally, actuating beam <b>31a</b> includes an anti-reset latch <b>29a</b> that is structurally and functionally substantially identical to latch <b>29</b> of actuator <b>30.</b> Actuator <b>30</b> further includes a mounting collar <b>77a</b> that is disposed and configured to mount slidably over proximal portions of hub <b>24.</b> Additionally, mounting collar <b>77a</b> is dimensioned for slidable disposition within holder <b>12a.</b> Actuator <b>30a</b> further includes an arm <b>90a</b> that projects distally from collar <b>77a.</b> Arm <b>90a</b> is dimensioned for slidable insertion in notch <b>17a</b> of holder <b>12a,</b> and terminates at an actuating button <b>92a.</b>

0088Needle assembly <b>10a</b> is assembled substantially as needle assembly <b>10,</b> described and illustrated above. However, collar <b>77a</b> of actuator <b>30a</b> is slidably disposed over and around proximal portions of hub <b>24a.</b> The subassembly of needle cannula <b>22,</b> hub <b>24,</b> packing shield <b>26,</b> holder <b>80</b> and actuator <b>30a</b> can be mounted in holder <b>12a</b> substantially as described above. However, arm <b>90a</b> will project slidably through notch <b>17a</b> such that actuating button <b>92a</b> is slidably disposed on the outer circumferential surface of holder <b>80a.</b>

0089Needle assembly <b>10a</b> is used substantially in the conventional manner as explained above. However, safety shield <b>28</b> is actuated by digital pressure exerted by a thumb or forefinger of the user on actuator button <b>92a.</b> In particular, the user urges actuator button distally along outer surface of holder <b>80</b> a sufficient distance for distal end <b>79a</b> of actuator <b>30a</b> to actuate safety shield <b>28</b> as explained above.

0090In certain instances, a user may want to have the ability to shield the needle cannula independently of the passive actuation described above with respect to the first embodiment. For example, a user may have some reason to terminate a specimen collection procedure prior to insertion of an evacuated tube into the holder. This objective can be achieved by alternate actuator <b>30b.</b> Actuator <b>30b</b> is effectively a hybrid of actuator <b>30</b> and actuator <b>30a.</b> Specifically, actuator <b>30b,</b> as shown in <figref idref="f0024">FIG. 28</figref>, is identical to actuator <b>30a</b> in all respects, but further includes a proximal end <b>78b</b> that is identical to proximal end <b>78</b> of actuator <b>30.</b> Thus, actuator <b>30b</b> permits shielding to be completed either by insertion of an evacuated tube into holder or by digital pressure an actuator button <b>92b.</b>

0091The internal disposition of safety shield <b>28</b> within the housing in any of these embodiments provides several significant advantages. In particular, a medical practitioner employing needle assembly <b>10</b> can hold needle assembly <b>10</b> much closer to distal end <b>32</b> of needle cannula <b>22.</b> This distal location for gripping needle assembly <b>10</b> provides better balance and feel for the medical practitioner and facilitates alignment and aiming of needle assembly <b>10.</b>

0092As an alternate to the embodiments described above, the needle assembly can be made in a detachable holder or hard pack assembly <b>100</b> configuration using all the components of the needle assembly described above with the addition of a non-patient needle shield <b>90</b> for enclosing proximal end <b>34</b> of needle cannula <b>22</b> shown in <figref idref="f0006 f0007">FIGS. 8-10</figref>. Non-patient needle shield <b>90</b> is reversibly detachable to one or both of needle housing <b>80</b> and hub <b>24.</b> The user removes non-patient needle shield <b>90</b> from hardpack assembly <b>100</b> and attaches holder <b>12</b> to the proximal end of housing <b>80</b> prior to use. Once holder <b>12</b> is attached to housing <b>80,</b> the user can remove packaging shield <b>26</b> and use the needle device in a similar manner to the needle assembly embodiment described herein.

0093A needle assembly in accordance with the subject invention is identified generally by the numeral <b>102</b> in <figref idref="f0025 f0026 f0027">FIGS. 29-31</figref>. Needle assembly <b>102</b> includes a hub <b>104</b> that is structurally and functionally very similar to the hub <b>24</b> identified and described above with respect to previous embodiments. Additionally, needle assembly <b>102</b> includes a needle housing <b>106</b> that is structurally and functionally very similar to needle housing <b>80</b> described and illustrated above. Hub <b>104</b> is connected to housing <b>106</b> substantially as hub <b>24</b> is connected to needle housing <b>80</b> in the embodiments described and illustrated in greater detail above. However, hub <b>104</b> differs from hub <b>24</b> in a few significant respects as described further below.

0094Hub <b>104</b> is molded unitarily from a transparent or translucent resin. Although hub <b>24</b> also could be molded from a transparent or translucent resin, the transparency of hub <b>24</b> was not critical to the embodiments described above. Hub <b>104</b> includes a proximal end <b>108</b> and a distal end <b>110.</b> A proximal passage <b>112</b> extends distally into proximal end <b>108</b> and a distal passage <b>114</b> extends proximally into distal end <b>110.</b> A flashback chamber <b>116</b> is defined in hub <b>104</b> between proximal and distal ends <b>108</b> and <b>110</b> and in communication with proximal and distal passages <b>112</b> and <b>114.</b> Hub <b>104</b> further includes a plug aperture <b>118</b> at a location intermediate proximal and distal ends <b>108</b> and <b>110</b> and extending transversely into hub <b>104</b> sufficiently to communicate with flashback chamber <b>116.</b> Needle housing <b>106</b> has a proximal end <b>120</b> and a distal end that is not shown in <figref idref="f0025 f0026 f0027">FIGS. 29-31</figref>. A notch <b>122</b> extends distally into proximal end <b>120</b> of needle housing <b>106.</b> A comparable notch (unnumbered) is illustrated in each of <figref idref="f0006">FIGS. 7</figref> and <figref idref="f0007 f0008">9-11C</figref> with respect to needle housing <b>80.</b> Hub <b>104</b> is connected to needle housing <b>106</b> in a manner to ensure that vent aperture <b>118</b> substantially aligns with notch <b>122</b> in needle housing <b>106.</b>

0095Needle assembly <b>102</b> further includes a vent plug <b>124</b> securely mounted in vent aperture <b>118.</b> Vent plug <b>124</b> includes a diaphragm <b>126</b> formed from a material that permits the passage of gas but not liquid. Diaphragm <b>126</b> may be formed with a plurality of microscopic openings or pores that are sufficiently small to permit passage of air molecules but will not permit passage of liquid molecules. Such diaphragms or filters are used elsewhere in the medical arts for situations where it is necessary to permit passage of a gas while preventing passage of a liquid. The alignment of vent aperture <b>118</b> with notch <b>122</b> ensures that vent plug <b>124</b> also will be aligned with notch <b>122.</b> Hence, needle housing <b>106</b> will not impede gas communication with vent plug <b>124.</b>

0096Needle assembly <b>102</b> further includes a proximal cannula <b>132</b> and a distal cannula <b>134.</b> Proximal cannula <b>132</b> has a pointed proximal end <b>136,</b> a distal end <b>138</b> and a lumen <b>140</b> extending between the ends. Portions of proximal cannula <b>132</b> near distal end <b>138</b> are mounted securely in proximal passage <b>112</b> of hub <b>104.</b> Thus, distal end of <b>138</b> of needle cannula <b>132</b> provides fluid communication with flashback chamber <b>116.</b> Distal cannula <b>134</b> includes a proximal end <b>142,</b> a distal end (not shown) and a lumen <b>144</b> extending between the ends. Proximal end <b>140</b> of distal cannula <b>134</b> is disposed in flashback chamber <b>116</b> and is spaced from distal end <b>138</b> of proximal cannula <b>132.</b> As a result, lumen <b>144</b> of distal cannula <b>134</b> and lumen <b>140</b> of proximal cannula <b>132</b> both communicate with flashback chamber <b>138.</b>

0097Needle assembly <b>102</b> can be used in the same manner as needle assembly <b>24</b> described and illustrated above. In particular, needle assembly <b>102</b> preferably includes a passive shielding mechanism that may be substantially the same as the shielding mechanism described and illustrated above. Thus, the distal end of distal cannula <b>134</b> can be placed in communication with a vein. Pressure of the blood in the vein will cause the blood to flow into lumen <b>144</b> of distal cannula <b>134.</b> The flowing blood will cause air that had been in lumen <b>144</b> and in flashback chamber <b>116</b> to pass through diaphragm <b>126</b> of vent <b>124.</b> Thus, there will not be an increasing air pressure that will restrict the flow of blood into lumen <b>144.</b> Sufficient flow of blood will cause the blood to fill lumen <b>144</b> and to flow into flashback chamber <b>116.</b> Hub <b>104</b> is formed from a transparent or translucent resin. Additionally, the holder <b>12</b> described and illustrated above also may be used with needle assembly <b>102</b> and typically is formed from a transparent material. Hence, the medical practitioner collecting the blood sample will be able to visually detect venous access by the presence of blood in flashback chamber <b>116.</b> This presence of blood will be apparent at flashback chamber <b>116</b> substantially before such venous access can be ascertained visually at a location proximally of proximal cannula <b>132.</b> Diaphragm <b>126</b> of vent plug <b>124</b> will not permit a flow of fluid therethrough. As a result, blood will continue flowing from flashback chamber <b>116</b> into lumen <b>140</b> of proximal cannula <b>132.</b> No blood will be permitted to escape from flashback chamber <b>116.</b>

0098The medical practitioner will insert an evacuated tube into the proximal end of holder <b>12</b> immediately after visual confirmation of venous access has been determined at flashback chamber <b>116.</b> As explained above, the stopper of the evacuated tube will move actuator <b>30</b> distally through actuator channel <b>56</b> of the hub as described above. This distal movement of actuator <b>30</b> will trigger the movement of safety shield <b>28</b> in a distal direction under the forces of the spring. Hence, the embodiment depicted in <figref idref="f0025 f0026 f0027">FIGS. 29-31</figref> have the advantages of passive actuation of a shielding mechanism as described above and further has the advantage of a very rapid indication of venous access.

0099It will be apparent that other variations can be made to the present invention without departing from the scope of the invention as defined by the appended claims. In alternate embodiments, the actuator can deflect a latch radial inwardly or in some other direction to effect disengagement from the housing. In addition, the actuator and the latch may be configured to generate rotation of the shield relative to the housing for disengaging a latch on the shield from a detent on the housing. Still further, other configurations for the exterior of the housing may be provided for convenient and secure digital manipulation, such as the exterior of the shield may include an array of ribs, grooves or dimples instead of or in addition to the flats shown in the illustrated embodiments. Furthermore other types of passive shielding activation can be combined with the flashback chamber and vent plug.